• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2011년도 추계 학술논문 발표대회
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• pp.175-176
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• 2011

Applying previous studies performed in the moisture transportation characteristics and shrinkage of lightweight concrete application of shrinkage reduction is to discuss. Applicability of shrinkage reduction effect of lightweight concrete applies for the analysis of PSC girder bridge beam placed on the construction site. Stress of the concrete bridge deck, rebar quantity is calculated by effective elastic modulus method and crack risk is assessed by moisture transport and differential shrinkage analysis. After approximately 10 days maximum tensile stress occurs 6MPa, similar to the case of normal concrete, a maximum tensile stress occurs 3MPa in lightweight concrete and comparing to normal concrete stress was reduced to approximately 50%. Normal and lightweight concrete crack index, respectively, is reduced 1.6 to 1.2, 1.2 to 0.9 in surface and boundary region. Therefore, reduction in shrinkage of concrete were able to confirm reduction of crack risk.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 춘계학술대회 논문집
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• pp.1050-1055
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• 2007

In the case of a rail road bridge extension work, especially single track to double track, the foundation of new substructure which supports the extended part of superstructure could be interfered by the exist foundation of an old bridge. When these two foundations are jointed to prevent such fatal effects of the structure as unequal subsidence of soil foundations, it is important to prove the structural behaviour of the joining surfaces between new foundation and old foundation. 3-Dimensional Finite Element Analysis Method have been studied for the solutions of the structural behaviour of the foundations. In this analysis, 'Contact Element' which allows the sliding of each adjoining member is used for the joint of the boundary surface of the old and new pier foundations. Furthermore, Material Nonlinear Behaviour Analysis also supports the accuracy of the result in this study because the foundations consist of concrete main bodies and reinforced steel bars. These detailed analyses secure the verification of the structural safety of the foundations in the extension work more firmly.

• 전자공학회논문지A
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• 제32A권12호
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• pp.136-141
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• 1995

GaAs power MESFETs with 1 .mu.m gate length and an undoped GaAs surface layer on the doped GaAs channel are fabricated using IR(image reversal) and air-birdge processes. And then We have measured and calculated DC and RF characteristics. We have obtained saturation current 107-500 mA (197-255 mA/mm), maximum linear RF output power 111-518.8 mW (204-270 mW/mm), current gain cut-off frequency 7-10 GHz, maximum unilateral transducer power gain 5.7-12.7, and power added efficiencies 37.9-41.2 % from the devices with gate width 0.45-2.2 mm, at 6 GHz.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2007년 추계학술발표대회 개요집
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• pp.218-221
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• 2007

The surface mounting technology of 0402 electric chip part is necessary to fabricate a high density and multi-functional module, but there is a limitation of the technology, like as a bridge and self-alignement. This work estimated SMT processing factors of 0402 chip. To obtain optimum SMT process, we evaluated effects of stencil thickness, shape of hole on printability and mountability. Printability shows best results under the thickness of $80{mu}m$ with circle hole shape and 90% square hole shape. In case of chip mounting process, chip mis-alignment and bridge was occurred rarely in same conditions. In more thin stencil thickness, $50{mu}m$, strength of 1005 chip parts was poor, because of amount of printed solder was insufficient.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1998년도 가을 학술발표회 논문집
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• pp.159-166
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• 1998

To study temperature effect of P.C. box girder bridge, field measurement was performed for six months, along with thermal analysis for the newly constructed viaduct of Gangbyun Highway in Seoul. Thermocouples were installed inside and surface of the flange and web of the box and temperature of box section md ambient temperature was measured. Measured environmental data are incorporated in finite element thermal analysis and computed temperature of the section was compared with measured one. Temperature gradient from thermal analysis was compared with Korean Highway Specification(1996)and the New Zealand Ministry of Works and Development code(1976). Thermal stress distribution across the box section was also compared.

• 한국도로학회논문집
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• 제15권5호
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• pp.101-110
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• 2013

PURPOSES : The purpose of this study is to evaluate the durability of ternary blended concrete mixtures adding ultra fine admixture. METHODS : From the literature review, crack was considered as the main distress failure criterion on concrete bridge deck pavement. To reduce the initial crack development due to drying shrinkage, CSA expansion agent and shrink reduction agent were used to ternary blended concrete mixtures as a admixture. Laboratory tests including chloride ion penetration test, surface scaling test, rapid freeze & thaw resistance test, non restrained drying shrinkage and restrained drying shrinkage test were conducted to verify the durability of ternary blended concrete mixtures. RESULTS : Based on the test results, proposed mixtures were verified as high qualified durable materials. Expecially initial drying shrinkage crack was not occurred in ternary blended concrete mixtures with CSA expansion agent. CONCLUSIONS : It is concluded that the durability of proposed ternary blend concrete mixture was acceptable to apply for the concrete bridge deck pavement.

• 드라이브 ㆍ 컨트롤
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• 제17권4호
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• pp.15-22
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• 2020

With the need for efficient maintenance technology to reduce maintenance costs for steel bridges, repainting robots are being developed to automate the work in narrow and poor bridge spaces. The repainting robot is equipped with a blasting module to remove paint layers and contaminants. This study developed a prototype monitoring module to be mounted on the repainting robot. The monitoring module analyzes the condition of the painting surface through a camera installed in the front, guides the direction of movement of the robot, and provides the operator with a video to check the working status after blasting through a camera installed in the back. Various image visibility enhancement technologies were applied to the monitoring module to overcome worksite challenges where incomplete lighting and dust occurs.

• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.224-229
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• 2009

Digital image recognition has been used for steel bridge surface assessment since late 1990s. However, the non-uniform illumination problems such as shades, shadows, and highlights are still challenges in image processing to date. Therefore, this paper develops a new approach to tackle the non-uniform illumination problem for rust image adjustment. The inhomogeneous illumination problem is divided into shades/shadows and highlights in this paper. The proposed BEMD-morphology approach (BMA) utilizes the bidimensional empirical mode decomposition to mitigate the shade/shadow effect, and the morphological processing to detect and replace the highlight area. Finally, the rust image processed with the BMA will be segmented by the K-Means algorithm, one of the most popular and effective methods, to show the effectiveness of illumination adjustment.

• 한국전산구조공학회논문집
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• 제32권5호
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• pp.313-322
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• 2019

교량에서의 화재는 최근까지도 빈번하게 발생되고 있으며, 특히 케이블교량에서 화재가 발생될 시 케이블에 높은 온도상승으로 인해 케이블에 손상 및 파단이 발생될 수 있다. 본 연구에서는 케이블교량에서 발생될 수 있는 화재 시나리오를 설정하였다. 또한 실물차량 화재실험 결과를 토대로 화재강도모델을 제안하여 대상교량 케이블의 열전달 해석을 수행하였다. 해석 결과 단면적이 작은 케이블에서 더 높은 온도상승이 발생되며, 유조차를 제외한 차종의 경우 내화 성능 기준을 초과하지 않는 결과를 나타내었다. 유조차 화재의 경우 갓길에서 발생될 때 최소 단면적 케이블에서 내화 성능 기준을 초과하는 결과를 보이며, 기준을 초과하는 케이블의 높이는 약 14m로 나타나 이에 따른 대책 및 내화 보강의 필요성을 확인하였다. 본 연구결과를 통해 케이블교량에서 화재가 발생될 때 케이블의 온도변화에 대한 간접적인 평가가 가능한 것을 확인하였으며, 향후 화재 발생 시 바람에 영향을 고려한 열전달 해석과 케이블의 온도상승 시 교량의 사용성에 대한 추가적인 연구가 필요할 것으로 판단된다.

• Earthquakes and Structures
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• 제10권5호
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• pp.1089-1109
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• 2016

Modified two-surface model (M2SM) is one of the steel elasto-plastic hysteretic constitutive models that consider both analysis accuracy and efficiency. However, when M2SM is used for complex strain history, sometimes the results are irrational due to the limitation of stress-strain path judgment. In this paper, the defect of M2SM was re-modified by improving the judgment of stress-strain paths. The accuracy and applicability of the improved method were verified on both material and structural level. Based on this improvement, the nonlinear time-history analysis was carried out for a deck-through steel arch bridge with a 200 m-long span under the ground motions of Chi-Chi earthquake and Niigata earthquake. In the analysis, we compared the results obtained by hysteretic constitutive models of improved two-surface model (I2SM) presented in this paper, M2SM and the bilinear kinematic hardening model (BKHM). Results show that, although the analysis precision of displacement response of different steel hysteretic models differs little from each other, the stress-strain responses of the structure are affected by steel hysteretic models apparently. The difference between the stress-strain responses obtained by I2SM and M2SM cannot be neglected. In significantly damaged areas, BKHM gives smaller stress result and obviously different strain response compared with I2SM and M2SM, and tends to overestimate the effect of hysteretic energy dissipation. Moreover, at some position with severe damage, BKHM may underestimate the size of seismic damaged areas. Different steel hysteretic models also have influences on structural damage evaluation results based on deformation behavior and low cycle fatigue, and may lead to completely different judgment of failure, especially in severely damaged areas.